The invention relates to new and useful compounds that are derivatives of isoindigo, indigo and indirubin. The invention further relates to the use of these derivatives in the treatment of cancer in animals.
Prevention and treatment of cancer has significantly improved in the United States during the past decade because of advancements in epidemiology, the technology of treatment, and the ability to deliver earlier diagnosis. Finding a cure for a diversity of cancers, such as lung, breast, prostate, colon and others however, is still a major challenge. Current approaches for the treatment of cancers are however, still limited to the lengthening of life, or the increase in the quality of life. Additionally, most meaningful therapeutics still have significant side effects. Therefore, it is imperative to find more effective therapeutic agents with lower side effects.
Tumor cells are characterized by uncontrolled cell proliferation due to the loss of the integration and coordination of extracellular signals with the cell cycle machinery. A typical cell cycle is classified into G1, S, G2 and M phases [1-3] and is illustrated in FIG. 2. In mammalian cells, proliferation is controlled in the G1 phase of the cell cycle. At the restriction point, cells can have different destinies. Examples of these cell destinies include: 1) leaving the cell cycle and entering a reversible quiescence phase; 2) exiting cell cycle and undergoing apoptosis; 3) differentiating and irreversibly exiting from the cell cycle; and 4) passing through the restriction point and becoming largely independent of extracellular signals and progress automatically through subsequent cell cycle phases (S, G2, M) to the next G1 phase. A variety of proteins are in turn responsible for the regulated progression of cells through the cell cycle. The key components of cell cycle machinery are the cyclins, the cyclin-dependent kinases (CDKs) and their inhibitors. Cyclins are a remarkably diverse family of proteins, which are synthesized from the mid/late of G1 phase till the M phase of the cell cycle and then rapidly degraded. A CDK typically contains a catalytic domain of 300 amino acids, which is inactive by it self. Cdks become active by binding to a cyclin. Activity of cdks is inhibited by their endogenous inhibitors (cdk inhibitors, or cdkIs include p15/p16/p18/p19 and p21/p27). Specific cyclin/CDK complexes are formed at specific stages of the cell cycle and their activities are required for progression of the cell cycle through S phase and mitosis.
Over-activation of CDKs is a character of a majority of human tumor cells. Strategies have been developed to modulate CDK activity for therapeutic intervention by either directly targeting the catalytic CDK subunit or indirectly affecting the CDK regulatory pathways [3]. Small molecule CDK inhibitors were designed to interact specifically with the ATP binding site of CDKs, such as flavopiridol congeners, polysulfates, toyocamycin derivatives, etc. Anticancer effects have been shown in clinical trials for those agents. Modulation of CDK activities can be achieved by regulating phosphorylation of CDKs or altering the expression of the CDKs or the their inhibitors (CKDIs). It is difficult to find specific modulators that do not interfere with other cell cycle components and do not affect normal cells.
A need thus exist for compounds that are easily produced and are highly effective at treating cancer but have minimal toxicity to normal cells.
Many Chinese herbs contain potent anti-cancer chemical components. For example, several Chinese plants such as Camptotheca acuminata (camptothecin), Cephalotaxus sp. (homoharringtonine/harringtonine) have provided compounds with significant antitumor activity [6]. PC-SPES, a mixture consisting of extracts from eight herbs for the treatment of prostate cancer, has been demonstrated to have potent anti-androgen activity [7]. Huanglian, a Chinese herbal extract, has recently been shown to inhibit cell growth by suppressing the expression of cyclin B1 and inhibiting CDC2 kinase activity in human cancer cells [8]. In addition, many Chinese herbal products have demonstrated an important role in cancer chemoprevention.
Studies have recently demonstrated that indirubin molecules from the anticancer Chinese herbxe2x80x94Qing Dai, exhibit their anticancer activity through modulating cyclin-dependent kinases [9].
Our previous studies demonstrated that meisoindigo, a second generation of indirubins, arrests leukemia cells at G1 phase, inhibits expression of oncogene c-myb, and induces cell differentiation and maturation at low concentrations (low toxicity) in which cell growth is completely inhibited without a decrease in cell viability [10, 11]. Recent studies demonstrate that indirubin selectively inhibits cyclin-dependent kinases (cdks) by competing with ATP for binding to the catalytic site of the kinase (FIG. 2) [12]. While these compounds have some utility, there still is a need for additional compounds that are effective for such treatments.
The present invention provides novel derivatives of isoindigo, indigo and indirubin that can be used to treat cancer in animals. These novel compounds exhibit minimal toxicity and side effect with a substantial chemotherapeutic index. These compounds allow for the treatment of a variety of cancers with minimal side affects experienced by the patient. Furthermore, the novel compounds are simple, stable chemical molecules that are substantially easy to produce and administer.
One of the advantages of the present invention is that the novel compounds have an increased solubility and bioavailability compared to the prior art molecules and thus are better suited for the treatment of cancer.
The present invention is directed to a specific group of novel compounds that are derivatives of isoindigo, indigo and indirubin as shown in formulas (I), (II) and (III) respectively 
and 
and 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, or R10 is independently a hydrogen, a monosaccharide, a disaccharide, a halogen, a hydrocarbyl group, or a functional hydrocarbyl group unsubstituted or substituted with one or more hydroxy moieties, carboxy moieties, nitroxy moieties, monosaccharides, disaccharides, amines, amides, thiols, sulfate, sulfonate, sulfonamide or halogens, wherein the hydrocarbyl has 1 to 12 carbon atoms.
A particularly preferred embodiment of the invention, referred to herein as NATURA, is the compound of the following Formula (IV) 
The present invention further provides a method of treating cancer and leukemia comprising administering to the animal a therapeutically effective amount of the novel derivatives of isoindigo and indirubin provided by the invention.
The present invention also provides pharmaceutical compounding that can be used to treat cancer or illnesses in an animal, comprising a therapeutically effective amount of a compound of the invention and a pharmaceutically acceptable carrier.